Method for controlling and/or monitoring a web-processing machine

ABSTRACT

A method for controlling and/or monitoring a web-processing machine ( 1 ) is introduced, wherein at least one web ( 5 ) of the web-processing machine ( 1 ) is unwound from the roll ( 12 ) of an unwinding device and is supplied to the machine ( 1 ), wherein the point in time (T) at which the web end on the roll is reached is determined and control signals are emitted depending on this point in time (T).  
     The novelty and inventive step of the invention is that the angular speed (ω) of the roll ( 12 ) and the speed (v) of the web ( 5 ) are recorded and that the point in time (T) is determined taking both these variables (v, ω) into consideration. A device ( 1 ) for implementing the method is also described and forms the subject of the patent request.

The invention relates to a method for controlling and/or monitoring a web-processing machine according to the preamble of claim 1.

Methods of this type are used inter alia in printing machines or bag machines. Often warning signals are emitted to call the machine operator's attention to the approaching end of the material web. However, semi-automatic or fully-automatic web-replacement methods are also known. In these methods, control signals must activate not only the signals but also other work steps of machines. Such control signals can also originate from a control unit programmed for this purpose.

The methods used for this purpose in accordance with prior art work unreliably. That is, they determine the point in time (T), at which the web end is reached, with extreme imprecision.

Therefore the object of the present invention is to provide a more reliable method. This object is achieved by the characterizing part of claim 1.

The angular speed of the roll can be measured in that suitable rotary encoders monitor the rotation movement of the roll and plot it against the time. The web speed can be recorded in a comparable manner with the help of rotary encoders, for example, on transport rollers, printing rollers or impression rollers. The diameter of these rollers usually remains constant while the roll is unwound as a result of which its diameter shrinks.

Generally the time or time measurement required for determining these two speeds means that a time segment is taken into consideration. This seems uncritical in the case of a continuous unwinding movement. But also in the case of discontinuous unwinding movements an averaging can take place over a time frame when determining the speed.

It is important that from the “web speed”, the length of the web unwound from the roll per time unit and then supplied usually to the processing part of the machine can be determined. This also applies to the recording of the rotary movement of the roll per time unit.

The same conclusion is arrived at if the rotary encoder is used on transport rollers, printing rollers or impression rollers to measure the length of the web section, which was drawn from the roll between two pulses delivered by the rotary encoder to the roll. For this purpose, the time elapsed between the two pulses delivered by the rotary encoder to the roll is also recorded.

Information about these two variables for the same periods of time can be processed in the inventive manner.

Thus, for example, the web length, which is measured by the web speed sensor during the rotation of a roll, corresponds to the circumference of the roll in this period of time. The circumference increases from rotation to rotation by an amount, which substantially corresponds to the thickness of the web material. The absolute disturbance variables, which result due to the start of the web and which are substantially constant in the case of the difference between the successive layers, inter alia play a role in this connection. Particularly these disturbance variables can be determined or even eliminated completely if the web thickness is determined in the manner described over a plurality of rotations.

It is advantageous if a control device implements the method in an automated form. For example, if the circumference of the winding sleeve—in case the roll comprises one such winding sleeve—is known to this control device, it can take this variable also into consideration when determining the point in time. If there is no winding sleeve present, a minimum circumference or diameter of the roll can be used in its place.

It is also very advantageous to use the inventive method in FFS machines as have been described in the German Patent Specification DE 199 20 478 A1. A tubular web is usually present in these methods.

The use of an inventive method in a machine in accordance with DE 199 20 478 A1 for controlling and/or monitoring the material roll on such a machine is included in the disclosure of the present document. Given the large material thickness of the flat tubular webs or side-gusseted tubular webs used there, the method described here is particularly advantageous.

Usually, in such an FFS machine a guide roller, whose rotary movement is monitored by a rotary encoder (incremental encoder), is used for determining the web speed or web length. This can take place in a similar manner in the case of printing machines.

Less slippage takes place on cylinders, which have a large web wrap-around. This increases the accuracy of the measurement.

In printing machines, however, it is also recommended to use printing cylinders or impression cylinders since particularly less slippage takes place here. There takes place particularly less web movement on central impression cylinders on which several rubber rollers or printing plate cylinders are placed. Central cylinder flexographic printing machines inter alia have such impression cylinders. They print inter alia flexible packaging material.

Additional example embodiments of the invention are specified in the present description and the claims.

The single FIGURE illustrates a schematic lateral view of an inventive device for implementing the inventive method.

The FIGURE illustrates schematically a web-processing machine 1. Such a machine can basically be a continuously operating machine, such as for example, a printing machine or a laminator or a machine operating at a given cycle rate, for example, an FFS machine, mentioned at the outset. Webs are supplied continuously to both the continuously operating machines as well as the machines operating at a given cycle rate. For this purpose, the web-processing machine 1 is equipped with a draw unit 2. This draw unit consists of a first roller 3 and a second roller 4, at least one of which is driven continuously. Both the rollers 3, 4 form a roller clearance through which the web 5 is conveyed in the web running direction z.

The machine 1 is illustrated in the FIGURE as a machine operating at a given cycle rate. For converting the continuous transport of the web 5 into a feed at a given cycle rate, the machine is equipped with a web storage unit 6, known per se, in which rolls 7 are mounted in a swivel arm 8, which is attached in a machine frame (not illustrated in detail), while the roll 9 is rotatably connected to the machine frame and is therefore stationary, however rotatable. At least one of the subsequent rolls 10 is driven intermittently and thus ensures the feed of the web 5 at a given cycle rate.

The web 5 is usually supplied to the web-processing machine 1 in the form of a web roll 12. For unwinding the web 5 from the web roll 12, the latter is non-rotatably connected to an axle 13, which penetrates through the winding sleeve 14 of the web roll 12 and which is mounted rotatably in the unwinding device 11. The unwinding device 11 can comprise at least one additional web roll (not illustrated in detail). The unwinding device 11 further comprises a joining station 15. This joining station 15 comprises a cross-cutting blade 16 using which the unnecessary web remainder can be cut off from the web end when or shortly before the web 5 is unwound completely from the web roll. The joining station 15 comprises additionally holding means 17, using which the start of a web which is wound up on another web roll, is held in a waiting position. If a tube is used as a web, this tube can be provided with slots in the region of its lateral edges, so that two walls separated from one another are formed at the web start 18. These walls can be folded over in vertical positions as illustrated in the FIGURE. In order to not have to mount the start 18 of the new web into the web-processing machine 1 when the web roll 12 is completely unwound, the web start 18 is joined to the end of the web 5 inside the joining station 15. For this purpose, a control device (not illustrated) receives or determines the point in time at which the web end on the web roll 12 is reached. Subsequently, the control device delivers control signals using signal lines (also not illustrated) to the joining station 15 and to the machine 1, if necessary. Activated by these signals, the web 5 is first drawn forward further in the web transport direction until a predetermined position is reached. Subsequently, the cross-cutting blade 16, if necessary, cuts off the web remainder from the end of the web 5, which is held on by clamping means 19. The holding means 17 now transport the web start 18 into a position, in which the longitudinal axis of the web 5 and that of the new web align with one another. Subsequently, the web start 18 is joined to the end of the web 5, for example by gluing or welding.

To ensure firstly that only the least possible web remainder remains on the web roll 12 and secondly that the web end is not drawn through the clamping means 19 or drawn past them, which would prevent or at least complicate the joining process of the end of the web 5 and the web start 18, it is necessary to predetermine as precisely as possible the point in time at which the web end on the web roll 12 is reached. In order to enable this, the unwinding device comprises a signal transmitter 20, which delivers a signal to the control device when the marking attached to the axle 13 passes the signal transmitter. The control unit can determine the angular speed ω of the web roll 12 from the number of signals and the associated elapsed time.

The signal transmitter can scan the marking in different ways, for example, optically, magnetically, electrically or mechanically. Other types of speed measurements are also applicable on such an unwinding device.

Furthermore, the control device obtains information about the web speed v. For this purpose, one of the rollers or rolls, which transport the web 5 continuously, is equipped with a rotary encoder. Preferably the roller 5 [sic] of the draw unit is equipped with the rotary encoder. The control unit can determine the instantaneous speed v of the web from the angle about which the roller or the roll moves per time unit and the circumference of the roller or the roll. Here also, other methods for determining the web speed are applicable.

The control unit can now determine the development of the circumference of the web roll 12 as a function of the time by comparing the speed v of the web with the angular speed ω of the web roll 12. Simple geometric relations are used as the basis for calculation. If the parameters of the winding sleeve 14, which allow inferences to be drawn about its outer diameter, are additionally known to the control unit, then the control unit can determine, precisely and in advance, the point in time T at which the end of the web 5 on the web roll 12 can be expected to be reached. The control unit can naturally calculate the length of the web 5 in advance, which can be still processed to the maximum extent. In this manner the web remainder is reduced while still enabling the joining process in the connection station 15. List of reference symbols  1 Web-processing machine  2 Draw unit  3 Roller  4 Roller  5 Web  6 Web storage  7 Roll  8 Swivel arm  9 Roll 10 Roll 11 Unwinding device 12 Web roll 13 Axle 14 Winding sleeve 15 Joining station 16 Cross-cutting blade 17 Holding means 18 Web start 18 19 Clamping means 20 Signal transmitter 21 Marking Z Web transport direction V Web speed ω Angular speed of the roll T Point in time at which the web end is reached 

1: Method for controlling and/or monitoring a web-processing machine (1), wherein at least one web (5) of the web-processing machine (1) is unwound from the roll (12) of an unwinding device and is supplied to the machine (1), wherein the point in time (T) at which the web end on the roll (12) is reached, is determined and wherein control signals are emitted depending on this point in time (T), said method being characterized in that the angular speed (ω) of the roll (12) is recorded, that the speed (v) of the web (5) is recorded, and that the point in time (T) is determined taking both these values (v, ω) into consideration. 2: Method according to claim 1, characterized in that when determining the point in time (T), the minimum diameter of the roll (12) and/or the diameter of the winding sleeve (14) are taken into consideration. 3: Method according to claim 1 characterized in that the material thickness of the web (5) is calculated from the development of the circumference of the roll (12) per rotation. 4: Method according to the preceding claim characterized in that the development of the circumference of the roll (12) is averaged over several rotations. 5: Method according to claim 3 characterized in that the material thickness is taken into account when determining the point in time (T). 6: Method according to claim 1 characterized in that the web speed (v) is measured using a rotary encoder, which records the rotations of a roller (3, 4), which is mechanically connected to the web (5). 7: Method according to the preceding claim, characterized in that the web speed is measured using a roller (3, 4), which rolls off with the web (5). 8: Web-processing machine (1) having an unwinding device (11), in which (1) at least one web (5) can be unwound from a roll (11) and can be supplied to the processing part of the machine (1), and also having a control device using which the point in time (T), at which the web end on the roll (12) is reached, can be determined, characterized by a means (20, 21) for recording the angular speed (ω) of the roll (11), a means for recording the speed (v) of the web (5), a control device using which both these values (v, ω) can be taken into consideration when determining the point in time (T). 9: Method according to claim 2, characterized in that the material thickness of the web (5) is calculated from the development of the circumference of the roll (12) per rotation. 10: Method according to claim 4, characterized in that the material thickness is taken into account when determining the point in time (T). 11: Method according to claim 2, characterized in that the web speed (v) is measured using a rotary encoder, which records the rotations of a roller (3, 4), which is mechanically connected to the web (5). 12: Method according to claim 3, characterized in that the web speed (v) is measured using a rotary encoder, which records the rotations of a roller (3, 4), which is mechanically connected to the web (5). 13: Method according to claim 4, characterized in that the web speed (v) is measured using a rotary encoder, which records the rotations of a roller (3, 4), which is mechanically connected to the web (5). 14: Method according to claim 5, characterized in that the web speed (v) is measured using a rotary encoder, which records the rotations of a roller (3, 4), which is mechanically connected to the web (5). 